Straight borehole drilling with automatic detecting and correcting means



July 21, 1964 T. F. GAsKELl. r-:TAL 3,141,512

STRAIGHT BOREHOLE DRILLING WITH AUTOMATIC DETECTING AND CORRECTING MEANS Filed Nov. 9, 1959 s sheets-sheet 1 THOMAS F. GASKELL BY EDWARD H.N.WATSON ATTORNEYS July 2l, 1954 T. F. GASKELL. ETAL 3,141,512

STRAIGHT BOREHOLE DRILL-ING WITH AUTOMATIC DETECTING AND CORRECTING MEANS Filed Nov. 9, 1959 s sheets-sheet s I f a? 4' sli 4 n?" INVENTORS: n; 9 THOMAS F. GASKELL ,o *il BY EDWARD H.N.wATsoN WWJM/ QL ATTORNEYS United States Patent O 3,141,512 STRAIGHT BOREHOLE DRILLING WITH AUT@- MA'llliC DETECTHNG AND CGRRECTWG MEANS Thomas Frohock Gaskell and Edward Henry Norman Watson, Sunbury-on-Thames, England, assignors to The British Petroleum Company Limited, London, England, a ioint-stock corporation of Great Britain Filed Nov. 9, 1959, Ser. No. 851,794 Claims priority, application Great Britain Nov. 19, 1958 8 Claims. (Cl. 175-26) This invention relates to an improved method of, and apparatus for use in, drilling boreholes in the earth.

It is Well known in oil drilling practice, when employing the usual type of rotary drilling system wherein the drilling bit is supported by, and rotates with, the drill pipe in the hole, that at depths greater than about 6000 feet it is dicult to penetrate the ground rapidly because the Weight on the bit required for rapid penetration causes the direction of the drill to depart from the vertical. Hitherto, it has not been possible to achieve direct steering of a drill which would be suitable for correcting the direction of a hole when it deviates from the vertical.

Recent years have seen the development of a number of new rotary drilling techniques, particularly rotary drilling techniques in which the motor which turns the drilling bit is near to the bit, enters the hole with the bit and advances with it. With this type of system, the drill pipe does not rotate (as it does in the more usual system) but serves to support both the motor and bit. Since it is essentially the combination of motor plus bit which does the drilling in this system, this combination may be considered as being a single unit and, for convenience, is hereinafter termed the drill or drill assembly; and when the motor is an hydraulic turbine, this combination is hereinafter termed, for convenience, a turbo-drill or turbo-drill assembly. Manifestly, Whether the bit-turning motor of this combination be an hydraulic turbine or an electric motor, it must comprise a stator part which is attached to the drill pipe and does not rotate, and a rotor part which is attached to the bit and does rotate. This non-rotating stator part may be, and, conventionally is, a casing for the rotor and bit and ordinarily serves as a means for attaching the drill or drill assembly to the lower end of the non-rotary drill pipe. The most important of these new rotary drilling techniques is turbo-drilling which is now widely used. Turbo-drilling has many advantages over normal rotary drilling; the main dilerence in the two techniques being, as mentioned above, that in turbo-drilling the drill pipe connecting the turbo-drill to the surface of the ground does not rotate. Another technique which avoids the necessity to rotate the drill pipe is electric drilling in which the bit is rotated electrically. The present invention is only applicable to this type of rotary drilling system in which the drill rotates relative to the drill pipe.

The principal object of the present invention is to provide a method of and apparatus for drilling the earth in a manner such that any deviation of the drill from a desired direction, e.g. the vertical, during drilling, is automatically corrected.

According to the invention, a method of making a borehole in the earth comprises drilling the earth with a drill having a motor-driven bit Which rotates relatively to the drill pipe, e.g. a turbo-drill, and which drill is connected to the drill pipe by means of a universal joint, detecting any deviation in the direction of travel of the drill from a desired direction by detecting means located in proximity to the drill, and applying a correcting force between the drill and drill pipe so as to return the drill to the desired direction of travel. The detecting means may be an inclinometer and the correcting force may be applied by a plurality of hydraulically-operated pistons Mice controlled by servo-valves which are actuated by signals from the inclinometer.

According to the invention, furthermore, apparatus for carrying out controlled directional drilling of the earth comprises a drill having a motor-driven bit adapted to be rotated relatively to a drill pipe, e.g. a turbo-drill, and connected to the drill pipe by means of a universal joint, detecting means located in proximity to the drill for detecting any deviation in the direction of travel of the drill from 'a desired direction during drilling, and correcting means for applying a correcting force between the drill and drill pipe when any such deviation occurs so as to return the drill to the desired direction of travel. The detecting means may be an inclinometer and the correcting means may comprise a plurality of hydraulicallyoperated pistons controlled by servo-Valves which are actuated by signals from the inclinometer.

The invention also consists in apparatus for controlling the direction in which a drill having a motor-driven bit which rotates relatively to the drill pipe travels when drilling the earth, comprising a iirst elongated member adapted for connection to a drill pipe, a second elongated member adapted for connection to the drill, the said elongated members being connected by a universal joint which allows relative angular movement between the two elongated members through a small angle in any direction from a position in which they are parallel to one another, correcting means secured to one of the elongated members for adjusting the relative angular positions of the elongated members, the correcting means being operatively connected to inclinometer means fixed in relation to one of the elongated members, the arrangement being such that, in the use of the apparatus, any deviation of the direction of travel of the second elongated member from a pre-selected direction is automatically corrected.

The correcting means may comprise two or more, and preferably three, double-acting pistons pivotally connected to one of the elongated members and spaced around its axis, the pistons being located in cylinders which are pivotally connected to the other elongated member and are adapted to be supplied with liquid under pressure on both sides of the pistons, an electro-hydraulic servo-valve being provided in association with each cylinder for controlling the supply of liquid to each side of the pistons in accordance with signals obtained in response to movements of the inclinometer.

The inclinometer may comprise a pendulum which operates directly or indirectly on a number of potentiometers, the number being the same as the number of pistons, each potentiometer being electrically connected to one of the servo-valves, the arrangement being such that, in the use of the apparatus, the valves are not operated when the elongated members are travelling in the desired direction, e.g. parallel to the pendulum, but such that any deviation of the elongated members from the desired direction causes electrical signals to be supplied to the servovalves from the potentiometers so as to cause the servovalves to energise the pistons hydraulically in such manner as to bring the elongated members back into the desired direction.

Advantageously the apparatus has three pistons spaced apart in a plane perpendicular to the axis of the elongated member to which they are connected, and three potentiometers located in the same angular positions as the pistons.

The supply of liquid under pressure to the cylinders may be provided by a pump driven by the drill in the use of the apparatus. Y

The invention will now be described by way of eX- ample by the accompanying drawings in which- FIGURES lA and 1B are longitudinal views, mainly in section, showing, respectively, a portion of the corn- 3 plete directional control assembly, attached to the lower sub of the drill pipe, and the remaining portion attached to a turbo-drill assembly, the views, taken together, showing the complete directional control assembly installed between the lower sub of the drill pipe and a turbo-drill assembly,

FIGURE 2 is a section along line A-A in FIGURE 1,

FIGURE 3 is a part section along line C-C in FIG- URE 1,

FIGURE 4 is an enlarged View of part of the mechanism,

FIGURE is a section along the line B-B in FIG- URE 1, and

FIGURE 6 is a fragmentary, exploded perspective view showing further details of the universal joint structure of FIGURE 2.

The complete directional control assembly I, as shown in FIGS. 1A and 1B, is assembled between the lower sub 2 of the drill pipe shown in FIG. 1A and a known type of turbo-drill assembly shown in FIG. 1B. The turbo-drill assembly 3, as depicted in FIG. 1B, comprises a non-rotating turbine stator part or turbine casing 3', which encloses the turbine rotor part 22 carrying a rotary drilling bit 3". The directional control assembly I comprises the elongated hollow lever arm member 4 which has a screwed connection at one end, its left-hand end as viewed in FIG. 1B, to the turbine casing 3 and serves as a lever arm for the turbo-drill assembly 3. The lever arm member 4 is pivotally connected adjacent its left-hand end as viewed in FIG. 1B, to the corresponding end of main casing 5 of the directional control assembly I, by a universal joint 6 composed of an inner sleeve 7, bearing stubs 8, centering washers 9, and slipresisting rubber seals I0. One pair of the bearing stubs 3, the horizontally disposed pair as viewed in FIG. 2, is pivotally connected to the main casing 5, and the other pair, the vertically disposed pair in FIG. 2, is pivotally connected to the lever arm 4, and all four stubs are connected with the inner sleeve 7. To this end, the righthand extremity of the outer or large diameter portion of the lever arm 4, as viewed in FIG. 1B, is tongued at diametrically opposite sides as is best seen in FIG. 6, to provide a pair of tongues 4 for pivotal movement of the lever arm 4 on the common axis of the pair of bearing stubs 8 which are shown as vertically arranged in FIG. 2. Likewise, the left-hand extremity of the main casing 5, as viewed in FIG. 1B, is tongued at diametrically opposite sides as is best seen in FIG. 6 to provide a pair of tongues 5 for pivotal movement of the lever arm 4 and inner sleeve '7, as a unit, on the common axis of the pair of bearing stubs 8 which are shown as horizontally arranged as viewed in FIG. 2 and are shown in exploded relationship to the tongue 5 in FIG. 6. The tongues of the main casing 5 and lever arm 4 are suitably spaced from each other circumferentially, as indicated in FIG. 2, to permit of the necessary freedom of angular movement of the lever arm 4 relative to the main casing 5, on the vertical and horizontal axes as seen in FIG. 2. The universal joint 6 allows complete freedom of movement of the turbo-drill assembly 3 and lever arm member 4 relative to the main casing 5, through a small angle.

The lever arm 4 passes through the centre of the universal joint 6 along the length of the mechanism main casing 5, the latter having a casing portion 33 and forming a first elongated member which is threadedly connected by the casing portion 33 to the lower sub 2 of the drill pipe. At the right-hand end of the lever arm 4, as viewed in FIG. 1A, are connected three double-acting pistons Il whose piston rods are pivotally mounted to the lever arm 4, these pistons being set radially 120 apart, as indicated in FIG. 3, and able to move in cylinders 12 which, in turn, pivot each on a pair of coaxial bearing stubs I3 and 13' paralleling the axis of the main casing 5. The retaining plate I4 of annular shape supports the bearing stubs 13 as indicated in FIGS. 1A and 3; the bearing stubs 13' being supported by the mechanism main casing 5 as indicated in FIG. lA.

Each cylinder 12 supports a manifold block 15 and an electro-hydraulic servo-valve 16 secured to the cylinders 12 by four screws (not shown). The valves are fed with oil at high pressure, and with electrical signals. The oil feed will be described iirst.

In the base of the hollow lever arm 4 is assembled a canister 17 containing a hydraulic pump 18 whose shaft 19 is rotated by a connection 20, incorporating a universal coupling 21, which is keyed to the top of the rotor 22 of the turbo-drill. Oil is drawn by the pump 18 from a reservoir 23, through inlet pipe 24 and circulated at high pressure from the pump to a filter 27 via outlet pipe 25 passing through the centre of reservoir 23. Immediately above the reservoir 23 is a relief valve 26 connected to the high pressure pump outlet pipe 25 by a by-pass pipe 26 serving to bypass the fluid from the pipe 25 back to the reservoir 23 when the required pressure is reached in the high pressure pipe 25. An accumulator (not shown) may be connected in the high pressure pipe 25 above the reservoir 23 if required.

The oil at high pressure flows into and through the lter 27 positioned intermediate the ends of the high pressure pipe 25, and then continues through the same pipe 25 into a sleeve 2S having an annulus 23 on its inside diameter and suitably sealed. Three hollow arms 29 lead from the annulus 28 at 120 from each other and connect the annulus to the manifold blocks 15 in which the arms 29 are mounted for axial sliding movement, one arm to each block. The manifold blocks I5 are suitably drilled to connect to their electro-hydraulic servo-valves 16 and cylinders 12 on either side of the pistons Il: Exhaust fluid expelled from the cylinders 12 by movement of the pistons Il is returned to the reservoir 23 via three hollow arms 30 which parallel the arms 29, are mounted in the blocks for axial sliding movement and connected with sleeve 3l which is concentric with sleeve 28 and has an annulus 31 on its inside diameter and suitably sealed. An annulus 32 formed by using a tube 32 concentric with and having a large inside clearance on the high pressure tube 25, returns the oil to the reservoir 23, by-passing the iilter 27 through the passages 27 on the way as shown. Holes are prepared in the part of the tube 32 located within the reservoir 23 to allow ow of oil into the reservoir.

The electrical signals to the valves will now be considered.

Positioned in upper casing 33 which is threadedly connected at its upper end to the sub 2 of the drill pipe and at its lower end to the upper end of the main casing 5, is an assembly 34 consisting of a housing 35 containing a power supply 36, and a pendulum-type inclinometer 38, The pendulum 39 is supported in a spherical-type bearing 40 to allow it freedom of movement in all directions, a stop 4I being provided to prevent any excess movement of the pendulum. The pendulum compartment 42 is lled with damping luid. Three potentiometers 43 are mounted 120 apart in the same angular positions as pistons 1I, with a stylus 44 from each potentiometer 43 in contact with the pendulum 39 as shown.

A voltage is applied from the power supply 36 such that a signal is fed from the potentiometers 43 to the electro-hydraulic servo control valve 16 in such a manner that the valves are not operated when outer casings l33, 5 and 3' are parallel to pendulum 39, i.e. when they are vertical. When these casings are not parallel to pendulum 39, signals are fed to the control valves 16 so as to energise pistons 11 hydraulicalIy to bring casings 3', 5 and 33 into line with pendulum 39, i.e. to return them to vertical.

The mud flow is indicated by the arrows 45 on FIG- URE 1. The free cross-sectional area through the mechanism at any point is equal to, or in excess of, the crosssectional area of the drill pipe above and as the mud flow is at a high velocity, guards 46 are provided to protect the moving parts as shown. Extra guards may be incorporated if desired.

The operation of the apparatus during drilling is as follows. With the turbo-drill vertical and drilling, oil at high pressure is transmitted by the pump 1S via the supply pipe 25 and hollow arms 29 to the electro-hydraulic servo-valves 16 which in turn distribute it to each side of the pistons 11, so making a hydraulic lock. There is no signal from the inclinometer potentiometers in this condition. When the whole lower assembly (1, 3) starts to deviate from vertical, a signal is transmitted from the potentiometers by virtue of the pendulum 39 staying vertical. The signal is amplified and fed to the servo valves 16. Pressure is then released to exhaust on the desired side of the pistons 11 via the arms 30 and sleeve 32' as required by the signal and a biased force is here applied by the pistons 11 to the upper end of the lever arm 4, which pivots at the universal joint 6 and creates a force at the bit to displace the lower end of the lever arm and thus the turbo-drill assembly 3. As the drill gradually corrects to vertical, the signal from the potentiometers reduces until it reaches zero. This automatic correction is continuous throughout the drilling time. It will be understood that, as the lever arm 4 pivots at the universal joint 6, the oil-circulating tubes 25 and 32 extending from the remote end of the lever arm, swing with the arm toward or away from the pivotally-mounted manifold blocks 15, thus causing the hollow arms 29 and 30 to move axially, and in a commensurate amount, further into or out of these blocks from the neutral position shown in FIGURE 4.

In the embodiment of the invention described above, the turbo-drill below the universal joint is constrained to be at all times parallel with the inclinometer pendulum i.e. to be vertical. The potentiometers may, however, be operated indirectly by a control arm, instead of directly from the pendulum, so as to constrain the turbo-drill to drill off vertical toy a pre-determined angle, this angle being equal to the pre-set angle between the control arm and the pendulum. Inclusion of a suitable azimuth reference (eg. a magnetic compass) with additional servo control for correcting positional errors Will allow the direction of the olf-vertical hole to be predetermined.

We claim:

1. Apparatus for carrying out controlled directional drilling of the earth, comprising a drill pipe; a drill having a motor including a non-rotary casing and having a bit adapted to tbe rotated by said motor relatively to the drill pipe; casing means adapted to be attached to said drill pipe; a lever arm member connected to said non-rotary casing; a universal joint flexibly connecting the non-rotary casing to the casing means; signal-generating detecting means located in said casing means in proximity to said lever arm member, for detecting any deviation in the direction of travel of the drill from a desired direction during drilling; and signal-responsive correcting means in said casing means, connected to said lever arm member and responsive to signals generated by said signalgenerating detecting means, for applying a correcting force to said lever arm member when any such deviation occurs, so as to return the drill to the desired direction of travel.

2. Apparatus according to claim l, in which the detecting means comprises a signal-generating inclinometer carried by said casing means, and in which the correcting means comprises signal-responsive servo-valves responsive to signals generated by said signal-generating inclinometer means, and in which said correcting means also comprises a plurality of hydraulically-operated pistons connected to said lever arm member and controlled by said servo-valves in response to signals from said inclinometer means.

3. Apparatus according to claim 2, in which the drill is a turbo-drill.

4. Apparatus for controlling the drilling direction of a drill having a motor including a non-rotary casing and having a bit which is driven by said motor and rotates relatively to a drill pipe, comprising a first elongated member providing a main casing adapted for connection to a drill pipe, a second elongated member received Within said casing and providing a lever arm adapted for connection to said non-rotary motor casing; a universal joint connecting said main casing and said nonrotary casing for relative angular movement between the two elongated members through a small angle in any direction from a position in which they are parallel to one another; signal-responsive correcting means within said main casing and secured to said lever arm for adjusting the relative angular positions of the elongated members; and signal-generating inclinometer means within said main casing and xed in relation to said lever arm and operatively connected to the correctingv means, for energizing said correcting means in response to any deviation of the direction of travel of the second elongated member from a pre-selected direction whereby said deviation is automatically corrected.

5. Apparatus according to claim 4, in which the correcting means comprise at least two double-acting pistons pivotally connected to said lever arm and spaced around its axis, a corresponding number of cylinders in which the pistons are located and which are pivotally connected to said main casing and adapted to be supplied with liquid under pressure on both sides of the pistons, and an electro-hydraulic servo-valve in association with each cylinder for controlling the supply of liquid to each side of the pistons in accordance with signals obtained in response to movements of said inclinometer means.

6. Apparatus according to claim 5, which includes a number of potentiometers and in which said inclinometer means comprises a pendulum which operates on said number of potentiometers, the number of potentiometers being the same as the number of pistons and each potentiometer being electrically connected to one of thev servo-valves, the arrangement being such that, in the use of the apparatus, the valves are not operated when the elongated members are travelling in the desired direction, but such that any deviation of the elongated members from the desired direction causes electrical signals to be supplied to the servo-valves from the poteniometers so as to cause the servo-valves to energize the pistons hydraulically in such manner as to bring the elongated members back to the desired direction.

7. Apparatus according to claim 6 in which there are three pistons spaced apart in a plane perpendicular to the axis of the elongated members to which they are connected and three potentiometers located in the same angular positions as the pistons.

8. Apparatus according to claim 5, comprising a pump for supplying liquid under pressure to the cylinders, the pump being adapted to be driven by said motor in the use of the apparatus.

References Cited in the le of this patent UNITED STATES PATENTS 1,313,367 Anschutz-Kaempfe Aug. 19, 1919 2,761,666 Heimaster et al Sept. 4, 6

FOREIGN PATENTS 215.563 Great Britain May 15, 1924 

1. APPARATUS FOR CARRYING OUT CONTROLLED DIRECTIONAL DRILLING OF THE EARTH, COMPRISING A DRILL PIPE: A DRILL HAVING A MOTOR INCLUDING A NON-ROTARY CASING AND HAVING A BIT ADAPTED TO BE ROTATED BY SAID MOTOR RELATIVELY TO THE DRILL PIPE; CASING MEANS ADAPTED TO BE ATTACHED TO SAID DRILL PIPE; A LEVER ARM MEMBER CONNECTED TO SAID NON-ROTARY CASING; A UNIVERSAL JOINT FLEXIBLE CONNECTING THE NON-ROTARY CASING TO THE CASING MEANS; SIGNAL-GENERATING DETECTING MEANS LOCATED IN SAID CASING MEANS IN PROXIMITY TO SAID LEVER ARM MEMBER, FOR DETECTING ANY DEVIATION IN THE DIRECTION OF TRAVEL OF THE DRILL FROM A DESIRED DIRECTION DURING DRILLING; AND SIGNAL-RESPONSIVE CORRECTING MEANS IN SAID CASING MEANS, CONNECTED TO SAID LEVER ARM MEMBER AND RESPONSIVE TO SIGNALS GENERATED BY SAID SIGNALGENERATING DETECTING MEANS, FOR APPLYING A CORRECTING FORCE TO SAID LEVER ARM MEMBER WHEN ANY SUCH DEVIATION OCCURS, SO AS TO RETURN THE DRILL TO THE DESIRED DIRECTION OF TRAVEL. 